Fermi surfaces of UB12

Physica B 165&166 (1990) 343-344 North-Holland

Fermi

Surfaces

Hisatomo Nobuyuki College

of UBlz

HARIMA, Akira YANASE, Yoshichika ONUKI*, NAGAI*, Kazuhiko SATOH’, Mitsuo KASAYAt of Integrated

*In&ate

of Physics,

tElec2ro2echnical

and Science, Universily of Osaka Prefecture, Science, University of Tdda, Tsukuba Ibaraki

Arts

of Material

TDepartment

Izuru UMEHARA’, Yoshiko and Fumitoshi IGAt

Tohoku

Laboratory,

Univer&y,

Tsukuba

Ibaraki

Sendai

Sakai 305,

Osaka

591,

KUROSAWA’,

Japan

Japan

980, Japan

305,Japan

We have measured the de Ham-van Alphen(dHvA) oscillation, and calculated the Fermi surfaces from the band structure of UB12. The angular dependence of the dHvA frequencies are consistent to the calculated extremal areas. Fermi surfaces consist of electron and hole ones, being a compensated metal. The measured cvclotron masses in the range of 0.6mo to 6mo are also agreement with the calculations.

UBlz is one of the cubic RBlz type compounds [l], where R is a heavy rare earth element, U, Pu, Np, Y and Zr. This material possesses a high melting point of 2235°C and is a congruently melting material. The previous magnetic susceptibility data show a Pauli paramagnetic nature, although the distance between the U atoms, 5.28A exceeds the Hill limit value of 3.4A. The electrical property is, however, small in knowledge. To clarify the Fermi surface (FS) property we have calculated the band structure and have measured the de Haas-van Alphen (dHvA) effect. We have carried out a energy band structure calculations of UBlz [2] using an LAPW method with an exchange and correlation potential in the local density approximation. Spin-orbit interactions are included in the sense of a perturbation for usual one-electron eigenstates including the other relativistic effects. The selfconsistent potential and the final band structure, as shown in fig.1, are given from eigenstates at 85 points in the irreducible Brillouin Zone, which are calculated using about 700 basis functions. 5f bands on U of UBlx have large band-width of about 0.2Ry, which is comparable to its spin-orbit interaction, because of its hybridization with Zp-electron on B. This itinerant character of 5f-electron on UBQ is consistent with its magnetic The Fermi level crosses two bands among behavior. these wide 5f bands, which have mainly j = 5/Z components. These two bands construct multiply connected FS as shown in fig.2. UBlz is a compensated metal and a number of the carrier is calculated as 0.317 for each hole and electron bands. The calculated specific heat K2 [3], while the expercoefficient y is lS.lmJ/mol

0921-4526/90/$03.50

UB,,

&

r*XXwQL*r

E

x

structure of UBlz in the vicinity Figure 1. Energy-band of the Fermi energy denoted by EF. imental 7 is 20mJ/mol . I<‘, so a mass enhancement factor is concluded about 1.65 in zero magnetic field. On the other hand, we have measured the dHvA oscillation in the filed up to 150kOe and temperature down to 0.45K. Figure 3 shows an angular dependence of the dHvA frequencies in the (100) and (110) planes. About fifteen branches are observed in a wide frequency range of lo6 Oe to 10s Oe. Calculated FS mentioned above explains the dHvA signals as follows. the (Y branch stems from the outside orbits on the empty tunnel centered at the X points in fig.2b. There are two candidates for the p branch, one is the inside orbits in the empty tunnel as mentioned above with the frequency of 3.90 x 10’ Oe, and the other is the orbits with the frequency of 4.86 x 10’ Oe on the center of the cube around r point in fig.2a. As the ,f? branch

@ 1990 - Elsevier Science Publishers B.V. (North-Holland)

H. Harima et al.

344

(4

(b)

Figure 2. Calculated

hole sheet (a) and electron

sheet (b) of the Fermi surface of UBiz

log 2-j

f~ branches. S branch has a large frequency, so it may be due to the orbits between 4 cubes through the slender arms. An opening around L point of electron FS causes an orbit of [ branch. The multiply connected electron FS has some other extremal areas, in which a orbit from L point to L point through E points may assigned to n branch. The measured cyclotron masses are in the range of 0.6 to 6mo. For example, the masses for the cr, p, 7, X, are 1.75(and 2.01), 1.93, 2.33, 1.00, respectively. On the other hand, they are roughly agreement with the calculated ones of 1.67, 2.8(and 2.6), 1.26, 1.11, respectively.

L

4

4

30



30 Field

Figure

3.

Angular



Angle

dependence

(Degree

90

We are grateful to professor T. Goto for a helpful discussion and providing us with the experimental data prior to publication. Numerical computation was performed at the Osaka University Computer Center and at t,he Computer Center of University of Osaka Prefecture. We have utilized a 16T-superconducting magnet at Cryogenic Center, University of Tsukuba. This work was supported by the project for ihe physics on actinide compounds, a Grand-in-Aid for Scientific Research on Priority Area from The Ministry of Education, Science and Culture, and by University of Tsukuba Project Research.

I

of dHvA

frequency

in

References

UBiz consists of two signals of 4.38 x 107 Oe and 4.29 x lo7 Oe, there is a possibility that two orbits mentioned above possesses the almost the same extremal areas. The v branch is accepted to the orbits on the cube in In fig.2a, the slender arms which is a little direction. thick around L points, may explain 7, L and K branches. Small two closed FS around I? point correspond to X and

1) P. Blum and F. Bertaut Acta. Crysta. 7 (1954) 81 2) H. Harima, S. Miyahara and A. Yanase, Physica in press a~ the proceedings of the International Conference on the Physics of the Highly Correlated Electron System, Santa Fe, 1989 3) l&nJ/mol. K2 reported as y value in 2) was roughly estimated.